Basics of Gratings (sinewave and square-wave)

A grating is a repeating sequence of light and dark bars. One adjacent pair of a
light and a dark bar makes up one cycle. These cycles repeat over and over in a grating.
Typically, we think of these gratings as having sharp edges like the bars shown in Figure
1 below.Figure 1. A grating composed of black and white bars that
is typically called a square-wave grating.

These gratings have become known as square-wave gratings because they have
characteristics like a square such as sharp edges. This square-like nature of the light
levels (or luminance), as it falls across different positions along the surface of an
object can be seen in Figure 2. Clicking on Figure 2 will bring down the square-wave
grating so that you can more easily compare the actual grating to the graph of the
grating.Figure 2. A graph of the luminance of
a square-wave as a function of position for one cycle.